LET’S GET PHYSICAL! In order for Russell Westbrook and the Thunder to avoid falling into a 3-1 hole tonight, they must get physical with Chris Bosh (left) and the Heat. Photo: AP

TIME TO SWITCH: Peter Vecsey says Thunder coach Scott Brooks must not allow Kevin Durant (right) to guard LeBron James if Oklahoma City wants to win the NBA title. (NBAE/Getty Images)

MIAMI — The Thunder have discovered what the Heat already knew and continue to demonstrate despite the Heat’s 2-1 series status: The first three rounds of playoff pressure is nothin’ compared to the stress and strain of the NBA Finals.

Except for the referees, whose calls remain consistently challenging to comprehend no matter how prominent the playoff round, no one is immune.

Not the kings of the court. Not the worker bees. And certainly not the esteemed coaches.

The Game 3 stat sheet showed the Heat winning Sunday by six after coming from 10 down and taking a two-point lead to close out the third quarter. But a look inside the ledger shows enough mental and physical errors to revolt the squeamish. Who better to bludgeon foremost than Scott Brooks? Whoever thought Erik Spoelstra was capable of outcoaching anybody? Then again, maybe it was a case of Brooks simply coaching incoherently.

One way or the other, either he changes some tactics and techniques tonight in Game 4, or the Thunder may as well call in sick Thursday for the formal detonation of LeBron’s predicted title wave.

Of paramount importance, Brooks must reassign Kevin Durant from LeBron to Shane Battier or whoever else is manning the third front-court position. Two straight games in foul trouble is two games too many, especially since it sentenced Durant to the dungeon for almost six minutes in the third quarter, which coincided with a 16-7 Heat wave.

We get the refs’ five-by-five message: Durant cannot go near LeBron or Dwyane Wade or be held by Chris Bosh on a screen without hearing a whistle blow in his disfavor … contrary to the other way around.

I’m guessing the meaning is equally loud and clear to Brooks.

More power to Durant for trying to defend the indefensible. And, no, guarding LeBron evidently did not adversely impact his finals’ record-breaking fourth-quarter production (17 and 16 points) in Games 1 and 2.

Still, it makes eminently more sense to devote the majority of his élan on offense (12 points in the final 12 minutes) and pray LeBrawn’s strength can be somewhat sapped, if not entirely zapped, trying to stick the league’s 3-time leading scorer.

This is one alteration — sic Thabo Sefolosha on LeBron — Brooks must make. Shiver me timbers if it’s not. That does not mean, of course, Durant’s visitation rights with LeBron should be permanently canceled. Waivers are always obtainable for special occasions.

Now let’s discuss some other numbskull decisions that helped advance the Heat halfway to paradise. Oops. Which brings us back to Brooks, who didn’t have a really good night.

He doesn’t seem to understand small-ball options … kept Derek Fisher on the ball far too long in Game 3 … should’ve reinserted Russell Westbrook when the Heat were making their third-quarter move … put Kendrick Perkins on the floor with 5:58 left on the game clock with no one he could guard … didn’t use Serge Ibaka, who might have been able to reroute James’ critical drive (2:18) at the halo.

Fittingly, I suppose, the Thunder’s final prayer session — down four with 16 seconds left — withered away when Brooks’ designated in-bounds passer, Sefolosha, la-di, la-di-da’d the delivery, which Wade intercepted.

“It’s a huge mistake when Brooks turns over the team to Fisher for extended periods,” underlines an NBA Finals war veteran. “He is a lieutenant not a general.

“He has not been a true point his whole career. His role is to cover [fourth-quarter steals on LeBron and Wade] and be a spot-up shooter. Never has been a good distributor (zero assists in 28:15) and creator.”

At times in Game 3, Fisher both lost track of his role and his mind. The lone member of Thunder Island owning fountains of finals experience — five championship rings — caved like it was a lockout negotiation.

Fisher unconscionably fouled James Jones on a deep dish later in the third after Ibaka had brain-locked moments earlier by sending Battier to the cash-checking line for three shots.

For his unspeakable encore, he hoisted a pull-up trey off an intermittent break midway into the fourth with the 24-point clock in its infancy without a teammate getting so much as a sniff.

My above source was left shaking his head. “That was totally out of line and completely out of character,” he muttered.

That brings us full cycle. It’s not as if the battled-tested (bad experience is better than none, I always say) Heat didn’t look rattled at crunch time. Playing “hot potato” … or hot “potatoe”, if you’re Dan Quayle … they committed nine turnovers in the last quadrant, two each by LeBron and Wade.

Lucky for them, their opponents are the wet-behind-the-finals-ears Oklahomans, who, aside from their abject stupidity, aborted nine of 24 free throws (62.5 percent) after leading the league (84 percent) in that category during the regular season.

Can the Heat handle having to play from ahead? I mean, down, 2-1, to Indiana and down, 3-2, to Boston brought out the best in Miami. Lest we forget, the Heat found themselves in the exact same position a finals ago against the Mavericks, though with Games 4 and 5 at Southfork, not South Beach.

This is Our Mr. Brooks’ first time in the finals compression chamber as both a player and a coach.